1876.] 13 [Hyatt. 



occupied by an extension of the endoderm, which he had called the 

 basal area. According to Barrois' observations, the hollow of segmen- 

 tation is retained during the planula stage in many species, and after 

 the cells have acquired the peculiar collars and flagelli, which are so 

 characteristic of the young, the cells around the open pole become very 

 much enlarged. When the sponge settles down at this pole, as it 

 eventually does, according to Barrois these enlarged cells form the 

 proper endoderm, or are continuous with this part when the endoderm 

 is formed in the interior, and fills up the segmentation hollow, as above 

 described in some of the earlier stages. Barrois does not figure this 

 area as distinctly as Carter does, but describes it, and also the origin 

 of the collar and spicules. These last originate in the granular mass 

 of the interior in Chalina, as 'well as in the true siliceous sponges, 

 and may be seen as bright points in the basal area. With regard to 

 their origin Prof. Hyatt, in this instance also, as in the other stages 

 described above, confirm vd Barrois' observations, that the spicules 

 do not originate from the transformation of cells, at least in the larva. 



Carter's observations and Barrois', show that the larva prefers to 

 attach itself by the collar and basal area to surfaces, and the latter 

 shows that this is due to the protrusion of the endoderm at this point. 

 Both Barrois and Carter have seen the larva becoming attached, and 

 studied the subsequent stages. Barrois has traced the formation of the 

 ampullaceous sacs in the endoderm, and the hollowing out between 

 them of the canal system, and the subsequent formation of the large 

 cloacal opening by which this system was connected with the exte- 

 rior. The effect of these observations is to confirm in the most 

 marked manner the views entertained by various writers of the great 

 taxonomic value of the characteristics of the Poriferae. 



Huxley was entirely in error with regard to the facts which he 

 employed to show this point, in so far as he separated the sponges 

 from the Metazoa, generally on account of their having many mouths 

 instead of one mouth, calling them Metazoa polystomata, in contrast to 

 the Metazoa monostomata. Nevertheless, he was the first to indicate 

 the great importance of the poriferous characteristic, and MacAllister 

 quotes him, therefore, as the authority for the Porifera3 or Polys- 

 tomata when he uses that word to designate for the first time a new 

 sub-kingdom of animals. 



This is, however, not a fair statement of the case, for not only 

 was Huxley in error with regard to his facts, but his estimate of 

 their taxonomic value was entirely too high. By his system, which 



